Catecholamines, parasympathetic stimuli, or cortisol for overwhelming sepsis?

Inflammation and exercise: Inhibition of monocytic intracellular TNF production by acute exercise via β2-adrenergic activation

Regular exercise is shown to exert anti-inflammatory effects, yet the effects of acute exercise on cellular inflammatory responses and its mechanisms remain unclear. We tested the hypothesis that sympathoadrenergic activation during a single bout of exercise has a suppressive effect on monocytic cytokine production mediated by β₂ adrenergic receptors (AR). We investigated the effects of 20-min moderate (65-70% VO₂ peak) exercise-induced catecholamine production on LPS-stimulated TNF production by monocytes in 47 healthy volunteers and determined AR subtypes involved. We also examined the effects of β-agonist isoproterenol and endogenous β- and α-agonists epinephrine and norepinephrine, and receptor-subtype-specific β- and α-antagonists on TNF production in a series of in vitro investigations. LPS-stimulated TNF production by peripheral blood monocytes was determined intracellularly by flow cytometry, using an intracellular protein transport inhibitor. Percent TNF-producing monocytes and per-cell TNF production with and without LPS was suppressed by exercise with moderate to large effects, which was reversed by a β₂-AR antagonist in spite that plasma TNF levels did not change. This inhibitory response in TNF production by exercise was mirrored by β-AR agonists in an agonist-specific and dose-dependent manner in vitro: similar isoproterenol (EC₅₀=2.1-4.7×10^-10M) and epinephrine (EC₅₀=4.4-10×10^-10M) potency and higher norepinephrine concentrations (EC₅₀=2.6-4.3×10^-8M) needed for the effects. Importantly, epinephrine levels observed during acute exercise in vivo significantly inhibited TNF production in vitro. The inhibitory effect of the AR agonists was abolished by β₂-, but not by β₁- or α-AR blockers. We conclude that the downregulation of monocytic TNF production during acute exercise is mediated by elevated epinephrine levels through β₂-ARs. Decreased inflammatory responses during acute exercise may protect against chronic conditions with low-grade inflammation.

Hypocortisolism in noncomatose patients during the acute phase of subarachnoid hemorrhage

BACKGROUND

Hypopituitarism represents a common long-term complication of subarachnoid hemorrhage (SAH). The incidence of hypocortisolism may be higher during the acute phase of SAH. Although hypocortisolism may be harmful in critically ill SAH patients, data are still lacking. The primary objective of this study was to investigate the incidence of hypocortisolism during the acute phase of SAH (15 days). Secondary objectives included an analysis of the relationship between hypocortisolism and outcome and the computation of the cortisol-time secretion curve.

METHODS

Clinical data of a consecutive series of 26 noncomatose patients with aneurysmal SAH were collected prospectively. The sample size was calculated considering an expected proportion of hypocortisolism of 30%, a confidence level of 95%, and a total width of confidence interval of 0.35. The definition of hypocortisolism (as taken from a statement from the critical care medicine task forces) includes random total cortisol <10 μg/dL or a Δtotal serum cortisol <9 μg/dL after 1 μg of corticotrophin hormone.

RESULTS

Hypocortisolism was diagnosed in 11 patients (42.3%). Cortisol increment after stimulation test was always >9 μg/dl, suggesting a hypothalamic-pituitary impairment. Hypocortisolism was independently associated with a higher risk of poor outcome (P = .046) even after adjusting for age and Hunt and Hess grade. The cortisol-time secretion curve showed a peak at day 5 and a minimum at day 8. The peak at day 5 correlated with the risk of delayed cerebral ischemia (P = .001), and the cortisol concentration slope between days 1 and 8 correlated with the risk of poor outcome (P = .033).

CONCLUSIONS

Patients with SAH are at high risk of secondary hypocortisolism during the first 15 days after bleeding. Hypocortisolism independently increases the risk of poor outcome. The acute phase of hypothalamo-pituitary dysfunction, as reflected by an abnormal day-by-day cortisol secretion pattern, may affect the risk of delayed cerebral ischemia.

Vasopressors and inotropes in the treatment of human septic shock: effect on innate immunity?

Catecholamines have been suggested to modulate innate immune responses in experimental settings. The significance hereof in the treatment of human septic shock is unknown. We therefore sought if and how vasopressor/inotropic doses relate to pro-inflammatory mediators during treatment of septic shock. We prospectively studied 20 consecutive septic shock patients. For 3 days after admission, hemodynamic variables, lactate and plasma levels of interleukins (IL)-6 and 8, tumor necrosis factor (TNF)-α, and elastase-α₁-antitrypsin were measured six hourly. Doses of vasoactive drugs were recorded. Of the 20 patients, nine died in the intensive care unit. Dobutamine doses were positively associated and related to TNF-α plasma levels, independently of disease severity, hemodynamics, and outcome, in multivariable models. Dopamine doses were positively associated with IL-6, and norepinephrine was inversely associated with IL-8 and TNF-α levels. Our observations suggest that catecholamines used in the treatment of human septic shock differ in their potential modulation of the innate immune response to sepsis in vivo. Dobutamine treatment may contribute to circulating TNF-α and dopamine to IL-6, independently of activated neutrophils. Conversely, norepinephrine may lack pro-inflammatory actions.